Cancerous pleural fluid is a common complication of cancer patients, mostly caused by the progression of tumor lesions and their recurrence and metastasis, but also the first symptom of cancer patients. The content of protein and lactate dehydrogenase in the pleural fluid is higher than normal, and the content of carcinoembryonic antigen in the pleural fluid is also significantly higher than normal. Malignant tumor cells can be detected in cancerous pleural fluid. For the treatment of cancerous pleural fluid, simple fluid extraction cannot provide good relief, and only systemic or local antitumor treatment can control cancerous pleural fluid well.